luacheck: fix warnings in test/app

Closes #5454

Reviewed-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Reviewed-by: Igor Munkin <imun@tarantool.org>

Co-authored-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Co-authored-by: Igor Munkin <imun@tarantool.org>

.luacheckrc

@@ -33,7 +33,7 @@ exclude_files = {
     -- Third-party source code.
     "src/box/lua/serpent.lua",
     "test-run/**/*.lua",
-    "test/app/**/*.lua",
+    "test/app/*.test.lua",
     "test/box/**/*.lua",
     "test/box-py/**/*.lua",
     "test/box-tap/**/*.lua",

test/app/fiber.result

@@ -560,11 +560,11 @@ space:drop()
 ---
 ...
 -- box.fiber test (create, resume, yield, status)
-dofile("fiber.lua")
+f = dofile("fiber.lua")
 ---
 ...
 -- print run fiber's test
-box_fiber_run_test()
+f()
 ---
 - - 'A: odd  1'
   - 'tester: status(printer) = suspended'

test/app/fiber.test.lua

@@ -215,9 +215,9 @@ fiber.self():name(old_name)
 space:drop()
 
 -- box.fiber test (create, resume, yield, status)
-dofile("fiber.lua")
+f = dofile("fiber.lua")
 -- print run fiber's test
-box_fiber_run_test()
+f()
 -- various...
 function testfun() while true do fiber.sleep(10) end end
 f = fiber.create(testfun)

test/app/lua/fiber.lua

@@ -70,11 +70,13 @@ end
 -- -------------------------------------------------------------------------- --
 
 -- run fiber test
-function box_fiber_run_test()
+local function box_fiber_run_test()
     -- run tester
     tester_task = fiber.create(tester_task_routine)
     while tester_task:status() ~= 'dead' do
         fiber.sleep(0)
     end
 	return result
 end
+
+return box_fiber_run_test